Recent years have seen tremendous growth in the number and variety of display devices available to the public. Computers (whether desktop, laptop, or notebook), personal digital assistants, mobile phones, and televisions having liquid crystal displays (LCD TVs) are but a few examples. Although some of these display devices are reflective display devices that utilize ordinary ambient light to view the display panel, most are transmissive display devices that require a light source to make the display panel visible.
Transmissive display devices fall into the categories of “edge-lit” or “direct-lit”. These categories differ in the placement of the light source relative to the display panel which defines the viewable area of the display device. In edge-lit display devices, a light source is disposed along an outer border of the display device, outside of the viewable area. The light source typically emits light into a light guide, a clear polymeric slab having length and width dimensions on the order of the viewable area, and from which light is extracted for illumination of the viewable area. In direct-lit display devices, a light source is disposed behind the viewable area, such that light emitted by the light source directly illuminates the viewable area. Some direct lit backlights also incorporate an edge-mounted light, and are thus capable of both direct lit and edge lit operation.